Evidence of rapid correlation‐based perceptual category learning by 4‐month‐olds

Young infants are very sensitive to feature distribution information in the environment. However, existing work suggests that they do not make use of correlation information to form certain perceptual categories until at least 7 months of age. We suggest that the failure to use correlation information is a by‐product of familiarization procedures that encourage infants to over encode individual exemplars rather than relations across exemplars. By changing the exemplar presentation regime to one in which exemplars are rapidly (2 s durations) and repeatedly presented we find that 4‐month‐olds can form perceptual categories on the basis of feature correlation information. In addition, this ability emerges rapidly between 114 and 134 days. We argue that the ability to process correlation information is present very early on but that the demonstration of that ability in categorization tasks is mediated by the demands of the task the infant is tested with. Copyright © 2005 John Wiley & Sons, Ltd.     

Development of category formation for faces differing by age in 9‐ to 12‐month‐olds: An effect of experience with infant faces

We examined category formation for faces differing in age in 9‐ and 12‐month‐olds, and the influence of exposure to infant faces on such ability. Infants were familiarized with adult or infant faces, and then tested with a novel exemplar from the familiarized category paired with a novel exemplar from a novel category (Experiment 1). Both age groups formed discrete categories of adult and infant faces, but exposure to infant faces in everyday life did not modulate performance. The same task was conducted with child versus infant faces (Experiment 2). Whereas 9‐month‐olds preferred infant faces after familiarization with child faces, but not child faces after familiarization with infant faces, 12‐month‐olds formed discrete categories of child and infant faces. Moreover, more exposure to infant faces correlated with higher novel category preference scores when infants were familiarized with infant faces in 12‐month‐olds, but not 9‐month‐olds. The 9‐month‐old asymmetry did not reflect spontaneous preference for infant over child faces (Experiment 3). These findings indicate that 9‐ and 12‐month‐olds can form age‐based categories of faces. The ability of 12‐month‐olds to form separate child and infant categories suggests that they have a more exclusive representation of face age, one that may be influenced by prior experience with infant faces.     

Joint attention and object learning in 5‐ and 7‐month‐old infants

We examined the effects of joint attention for object learning in 5‐ and 7‐month‐old infants. Infants interacted with an adult social partner who taught them about a novel toy in two conditions. In the Joint Attention condition, the adult spoke about the toy while alternating gaze between the infant and the toy, while in the Object Only condition, the adult looked to the toy and to a spot on the ceiling, but never at the infant. In the test trials following each social interaction, we presented infants with the ‘familiarization’ toy and a novel toy, and monitored looking times to each object. We found that 7‐month‐olds looked significantly longer to the novel toy following the Joint Attention relative to the Object Only condition, while 5‐month‐old infants did not show a significant difference across conditions. We interpret these results to suggest that joint attention facilitated 7‐month‐old infants' encoding of information about the familiarization object. Implications for the ontogeny of infant learning in joint attention contexts are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Individual differences in 10‐month‐olds' performance on the A‐not‐B task

This study used the classical A‐not‐B task (Piaget, 1954 ) to explore individual differences in cognitive flexibility in 10‐month‐old infants by: (1) examining how differences in search performance during A trials relate to search performance during B trials; (2) studying the relation between temperamental dimensions and A‐not‐B performance; and (3) investigating differences in search performance between looking and reaching responses within the same task. Forty infants were tested on a fixed‐design‐version of the A‐not‐B task, not allowing for training or individual adjustment, but instead eliciting additional search behaviors than the common correct responses in A trials and perseverative errors in B trials. Infants were also rated by their parents on the temperamental scales Activity level and Attention span. The main findings were: (1) performance on A trials affected B trial performance, with infants being more correct on A trials having more incorrect and less ‘no search’ responses on B trials; (2) activity level, but not attention span, was related to performance on the A‐not‐B task, with infants performing better on A trials having a lower activity level; and (3) there were a few differences in performance with regard to modality, indicating that responding correctly by looking may be less cognitively demanding than doing so by reaching. This study demonstrated that 10‐month‐olds show a wide variation of search behaviors on this A‐not‐B task, resulting in individual differences in performance. These differences are suggested to reflect variation in temperamental activity level as well as maturity of short term/working memory, inhibition and cognitive flexibility.     

Humour Perception and Creation between Parents and 3‐ to 6‐month‐old Infants

Humour and laughter are universal to the human psychological experience and have serious developmental and evolutionary implications. Despite the early emergence of laughter in infancy, infants have been largely ignored in the humour research and humour has been largely ignored in the infant research. The present study describes the emergence of humour perception and creation in a sample of 20 parent–infant dyads who were followed from ages 3‐to‐ 6 months. The study examined how infants discover that absurd nonverbal behaviour, known as ‘clowning’, is amusing in the context of social engagement with caregivers. Results indicate that parents primarily use clowning when attempting to amuse their infants and pair these behavioural absurdities with affective cues like smiling and laughing. As they got older, infants were more likely to laugh and smile in response to clowning. Infants' ability to create humor via clowning also increased with age, starting with simple shrieks at 3 months to imitating absurd actions by 5 months. These increases are partly potentially explained by accompanying increases in parental smiling, laughing and clowning in response to infant clowning. Future research should employ more diverse samples and experimentally investigate the role of parental affect and social referencing in infants' interpretation of absurd behavior. Copyright © 2011 John Wiley & Sons, Ltd.     

Heart rate reactivity during contingency learning in 5‐ to 10‐month‐old at‐risk and non‐risk babies

The study investigated the dynamic relation between contingency learning and heart rate with risk and non‐risk babies 5‐ to 10‐months‐old. Four groups were compared in a two contingency treatments (contingent, yoked) × two risk status design. Concurrent heart rate was monitored during three phases of a contingency learning task (baseline, contingency/stimulation, extinction) and analysis focused on phase transitions. Non‐risk babies presented with contingent stimulation showed an immediate increase in cardiac rate associated with a subsequent response increase to the contingency. Risk infants presented with contingent stimulation showed delayed cardiac reactivity accompanied by a smaller response increase to the contingency. Yoked controls decreased responding in the contingent period with no significant changes in cardiac reactivity at phase transitions. The findings of the study are discussed in relation to individual differences in physiological regulation and to differential sensitization in a contingency learning task.     

Categorization and understanding of facial expressions in 4‐month‐old infants

This study examined whether 4‐month‐olds (N = 40) could perceptually categorize happy and angry faces, and show appropriate behavior in response to these faces. During the habituation phase, infants were shown the same type of facial expressions (happy or angry) posed by three models, and their behavior in response to those faces was observed. During the test phase immediately after the habituation phase, infants saw a novel emotional expression and a familiar expression posed by a new model, and their looking times were measured. The results indicated that, although 4‐month‐olds could perceptually categorize happy and angry faces accurately, they responded positively to both expression types. These findings suggest that, although infants can perceptually categorize facial expressions at 4 months of age, they require further time to learn the affective meanings of the facial expressions.     

A little labeling goes a long way: Semi‐supervised learning in infancy

There is considerable evidence that labeling supports infants' object categorization. Yet in daily life, most of the category exemplars that infants encounter will remain unlabeled. Inspired by recent evidence from machine learning, we propose that infants successfully exploit this sparsely labeled input through “semi‐supervised learning.” Providing only a few labeled exemplars leads infants to initiate the process of categorization, after which they can integrate all subsequent exemplars, labeled or unlabeled, into their evolving category representations. Using a classic novelty preference task, we introduced 2‐year‐old infants (n = 96) to a novel object category, varying whether and when its exemplars were labeled. Infants were equally successful whether all exemplars were labeled (fully supervised condition) or only the first two exemplars were labeled (semi‐supervised condition), but they failed when no exemplars were labeled (unsupervised condition). Furthermore, the timing of the labeling mattered: when the labeled exemplars were provided at the end, rather than the beginning, of familiarization (reversed semi‐supervised condition), infants failed to learn the category. This provides the first evidence of semi‐supervised learning in infancy, revealing that infants excel at learning from exactly the kind of input that they typically receive in acquiring real‐world categories and their names.     

Preferential orienting to faces in 4‐month‐olds: analysis of temporal–nasal visual field differences

A two‐process theory of the development of face processing predicted that newborns’ preferential orienting to face‐like patterns would be stronger in the temporal visual field than in the nasal. This prediction was confirmed in a previous study. While it is known that the newborn tendency to orient to face‐like patterns declines around 6 weeks of age, it is not known whether this is due to inhibition by cortical pathways or to the conflicting biases of cortical and subcortical pathways. In the present experiment we repeated the newborn study but with 4‐month‐olds and obtained results which were partially consistent with both the inhibition and the conflicting pathways accounts. We conclude that disappearance of the newborn tendency to orient to face‐like patterns is probably due to multiple factors.     

The value of proactive goal setting and choice in 3‐ to 7‐year‐olds' use of working memory gating strategies in a naturalistic task

Rule‐guided behavior depends on the ability to strategically update and act on content held in working memory. Proactive and reactive control strategies were contrasted across two experiments using an adapted input/output gating paradigm (Neuron, 81, 2014 and 930). Behavioral accuracies of 3‐, 5‐, and 7‐year‐olds were higher when a contextual cue appeared at the beginning of the task (input gating) rather than at the end (output gating). This finding supports prior work in older children, suggesting that children are better when input gating but rely on the more effortful output gating strategy for goal‐oriented action selection (Cognition, 155, 2016 and 8). A manipulation was added to investigate whether children's use of working memory strategies becomes more flexible when task goals are specified internally rather than externally provided by the experimenter. A shift toward more proactive control was observed when children chose the task goal among two alternatives. Scan path analyses of saccadic eye movement indicated that giving children agency and choice over the task goal resulted in less use of a reactive strategy than when the goal was determined by the experimenter.     

“I don't know but I know who to ask”: 12‐month‐olds actively seek information from knowledgeable adults

Active social communication is an effective way for infants to learn about the world. Do pre‐verbal and pre‐pointing infants seek epistemic information from their social partners when motivated to obtain information they cannot discover independently? The present study investigated whether 12‐month‐olds (N = 30) selectively seek information from knowledgeable adults in situations of referential uncertainty. In a live experiment, infants were introduced to two unfamiliar adults, an Informant (reliably labeling objects) and a Non‐Informant (equally socially engaging, but ignorant about object labels). At test, infants were asked to make an impossible choice—locate a novel referent among two novel objects. When facing epistemic uncertainty—but not at other phases of the procedure—infants selectively referred to the Informant rather than the Non‐Informant. These results show that pre‐verbal infants use social referencing to actively and selectively seek information from social partners as part of their interrogative communicative toolkit. A video abstract of this article can be viewed at https://youtu.be/23dLPsa-fAY     

Face detection in 2‐ to 6‐month‐old infants is influenced by gaze direction and species

Humans detect faces efficiently from a young age. Face detection is critical for infants to identify and learn from relevant social stimuli in their environments. Faces with eye contact are an especially salient stimulus, and attention to the eyes in infancy is linked to the emergence of later sociality. Despite the importance of both of these early social skills—attending to faces and attending to the eyes—surprisingly little is known about how they interact. We used eye tracking to explore whether eye contact influences infants' face detection. Longitudinally, we examined 2‐, 4‐, and 6‐month‐olds' (N = 65) visual scanning of complex image arrays with human and animal faces varying in eye contact and head orientation. Across all ages, infants displayed superior detection of faces with eye contact; however, this effect varied as a function of species and head orientation. Infants were more attentive to human than animal faces and were more sensitive to eye and head orientation for human faces compared to animal faces. Unexpectedly, human faces with both averted heads and eyes received the most attention. This pattern may reflect the early emergence of gaze following—the ability to look where another individual looks—which begins to develop around this age. Infants may be especially interested in averted gaze faces, providing early scaffolding for joint attention. This study represents the first investigation to document infants' attention patterns to faces systematically varying in their attentional states. Together, these findings suggest that infants develop early, specialized functional conspecific face detection.     

Nine‐ to 11‐month‐old infants' reasoning about causality in anomalous human movements1

Two habituation experiments investigated 9–11‐month‐old infants' reasoning about causality in anomalous human movements. During habituation, infants saw an event in which a person walked toward a stationary person behind an occluder who fell down after an interval. Then, the infants were tested with two events without the occluder: the contact event in which the first person pushed the second one to fall down and the no‐contact event in which the second person fell down without any contact. In Experiment 1, in which the persons were face‐to‐back, infants looked at the no‐contact event for a longer time, whereas in Experiment 2, in which the persons were face‐to‐face, they looked at both the events for equal duration. Thus, infants considered it unnatural when a person fell down without external force in the absence of any action from a distance (e.g. communication). Infants seem to apply the physical contact principles to human movements in certain cases.     

Cerebral blood flow in 5‐ to 8‐month‐olds: Regional tissue maturity is associated with infant affect

Infancy is marked by rapid neural and emotional development. The relation between brain function and emotion in infancy, however, is not well understood. Methods for measuring brain function predominantly rely on the BOLD signal; however, interpretation of the BOLD signal in infancy is challenging because the neuronal‐hemodynamic relation is immature. Regional cerebral blood flow (rCBF) provides a context for the infant BOLD signal and can yield insight into the developmental maturity of brain regions that may support affective behaviors. This study aims to elucidate the relations among rCBF, age, and emotion in infancy. One hundred and seven mothers reported their infants' (infant age M ± SD = 6.14 ± 0.51 months) temperament. A subsample of infants completed MRI scans, 38 of whom produced usable perfusion MRI during natural sleep to quantify rCBF. Mother‐infant dyads completed the repeated Still‐Face Paradigm, from which infant affect reactivity and recovery to stress were quantified. We tested associations of infant age at scan, temperament factor scores, and observed affect reactivity and recovery with voxel‐wise rCBF. Infant age was positively associated with CBF in nearly all voxels, with peaks located in sensory cortices and the ventral prefrontal cortex, supporting the formulation that rCBF is an indicator of tissue maturity. Temperamental Negative Affect and recovery of positive affect following a stressor were positively associated with rCBF in several cortical and subcortical limbic regions, including the orbitofrontal cortex and inferior frontal gyrus. This finding yields insight into the nature of affective neurodevelopment during infancy. Specifically, infants with relatively increased prefrontal cortex maturity may evidence a disposition toward greater negative affect and negative reactivity in their daily lives yet show better recovery of positive affect following a social stressor.     

Infant gaze following depends on communicative signals: An eye‐tracking study of 5‐ to 7‐month‐olds in Vanuatu

Gaze is considered a crucial component of early communication between an infant and her caregiver. When communicatively addressed, infants respond aptly to others’ gaze by following its direction. However, experience with face‐to‐face contact varies across cultures, begging the question whether infants’ competencies in receiving others’ communicative gaze signals are universal or culturally specific . We used eye‐tracking to assess gaze‐following responses of 5‐ to 7‐month olds in Vanuatu, where face‐to‐face parent–infant interactions are less prevalent than in Western populations. We found that—just like Western 6‐month‐olds studied previously—5‐ to ‐7‐month‐olds living in Vanuatu followed gaze only, when communicatively addressed. That is, if presented gaze shifts were preceded by infant‐directed speech, but not if they were preceded by adult‐directed speech. These results are consistent with the notion that early infant gaze following is tied to infants’ early emerging communicative competencies and rooted in universal mechanisms rather than being dependent on cultural specificities of early socialization.     

Non‐Bayesian Noun Generalization in 3‐ to 5‐Year‐Old Children: Probing the Role of Prior Knowledge in the Suspicious Coincidence Effect

It is unclear how children learn labels for multiple overlapping categories such as “Labrador,” “dog,” and “animal.” Xu and Tenenbaum (2007a) suggested that learners infer correct meanings with the help of Bayesian inference. They instantiated these claims in a Bayesian model, which they tested with preschoolers and adults. Here, we report data testing a developmental prediction of the Bayesian model—that more knowledge should lead to narrower category inferences when presented with multiple subordinate exemplars. Two experiments did not support this prediction. Children with more category knowledge showed broader generalization when presented with multiple subordinate exemplars, compared to less knowledgeable children and adults. This implies a U‐shaped developmental trend. The Bayesian model was not able to account for these data, even with inputs that reflected the similarity judgments of children. We discuss implications for the Bayesian model, including a combined Bayesian/morphological knowledge account that could explain the demonstrated U‐shaped trend.     

Perceptual Learning of Intonation Contour Categories in Adults and 9‐ to 11‐Year‐Old Children: Adults Are More Narrow‐Minded

We report on rapid perceptual learning of intonation contour categories in adults and 9‐ to 11‐year‐old children. Intonation contours are temporally extended patterns, whose perception requires temporal integration and therefore poses significant working memory challenges. Both children and adults form relatively abstract representations of intonation contours: Previously encountered and novel exemplars are categorized together equally often, as long as distance from the prototype is controlled. However, age‐related differences in categorization performance also exist. Given the same experience, adults form narrower categories than children. In addition, adults pay more attention to the end of the contour, while children appear to pay equal attention to the beginning and the end. The age range we examine appears to capture the tail‐end of the developmental trajectory for learning intonation contour categories: There is a continuous effect of age on category breadth within the child group, but the oldest children (older than 10;3) are adult‐like.     

The neural correlates of orienting to walking direction in 6‐month‐old infants: An ERP study

The ability to detect social signals represents a first step to enter our social world. Behavioral evidence has demonstrated that 6‐month‐old infants are able to orient their attention toward the position indicated by walking direction, showing faster orienting responses toward stimuli cued by the direction of motion than toward uncued stimuli. The present study investigated the neural mechanisms underpinning this attentional priming effect by using a spatial cueing paradigm and recording EEG (Geodesic System 128 channels) from 6‐month‐old infants. Infants were presented with a central point‐light walker followed by a single peripheral target. The target appeared randomly at a position either congruent or incongruent with the walking direction of the cue. We examined infants' target‐locked event‐related potential (ERP) responses and we used cortical source analysis to explore which brain regions gave rise to the ERP responses. The P1 component and saccade latencies toward the peripheral target were modulated by the congruency between the walking direction of the cue and the position of the target. Infants' saccade latencies were faster in response to targets appearing at congruent spatial locations. The P1 component was larger in response to congruent than to incongruent targets and a similar congruency effect was found with cortical source analysis in the parahippocampal gyrus and the anterior fusiform gyrus. Overall, these findings suggest that a type of biological motion like the one of a vertebrate walking on the legs can trigger covert orienting of attention in 6‐month‐old infants, enabling enhancement of neural activity related to visual processing of potentially relevant information as well as a facilitation of oculomotor responses to stimuli appearing at the attended location.